I usually use an image I've doctored in Photoshop CS4. It's easy to upload and drop it in the contant contant image library. I'm sure you could use any graphics program that allows you to modify images.
You can also layer text in the Library tab of your account. While in your Library, click on an image, then on the left under the thumbnail click to edit. Then with our Adobe Creative SDK editing tools you can use the text tool. When you’re finished adding your text you can save your edits and insert your new image into your campaign.
Thanks! Marissa W. Community & Social Media Support Representative